1. Field of the Invention
The present invention relates to a liquid crystal display device modulating light for picture display.
2. Description of Related Art
Recently, a liquid crystal display device is mainly used as a display monitor of a television, a notebook computer, a car navigation device or the like. The liquid crystal display device is classified into various modes (types) depending on arrangement of liquid crystal molecules between panel substrates of the device. For example, a TN (Twisted Nematic) mode and an IPS (In-Plane Switching) mode are listed. In addition, an OCB (Optically Compensatory Bend) mode and a VA (Vertically Aligned) mode are listed. In particular, a VA-mode liquid crystal display device is now noticed because high contrast is easily achieved thereby.
The VA-mode liquid crystal display device has a liquid crystal display panel 100 and a light source 101, for example, as illustrated in FIG. 23. The liquid crystal display panel 100 has a vertically-aligned liquid crystal layer 130 enclosed between a drive substrate 110 and a counter substrate 120 having a color filter 121 with pixel electrodes 111 and counter electrodes 122, and a pair of vertical alignment films 112 and 123 in between. A pair of polarizing plates 102 and 103 are disposed outside the drive substrate 110 and the counter substrate 120, respectively such that transmission axes of the polarizing plates 102 and 103 are perpendicular to each other. The liquid crystal display device modulates light (white light) from the light source 101 by the liquid crystal display panel 100 for picture display.
However, when such liquid crystal display device is in white display, the following difficulty occurs: a hue seen from a visual point in a vertical direction (Z-axis direction) to a substrate surface (XY plane) is different from a hue seen from a visual point in a direction (an oblique direction) oblique to the vertical direction. In detail, a hue of light L101 is white in white display, the light entering in a vertical direction from the light source 101 to the liquid crystal display panel 100, and being emitted in the vertical direction. In contrast, a hue of light L102 is yellowish white, the light entering in an oblique direction from the light source 101 to the liquid crystal display panel 100, and being emitted in approximately the same direction as the oblique direction. The reason why the light color is seen to be yellowish in this way is considered to be because light entered in an oblique direction to a substrate surface is changed in hue mainly in the liquid crystal layer 130 and then emitted in the oblique direction.
To solve the difficulty, a technique is known, where a dichromatic-dye-containing sheet is provided between a liquid crystal display panel and a light source (see Japanese Patent No. 2861982). The dichromatic-dye-containing sheet is formed by using approximately rod-like dichromatic dye, a liquid-crystalline substance such as polymeric liquid crystal or liquid crystal molecules, and ultraviolet curing resin such that long axis directions of the dichromatic dye are arranged (aligned) at a predetermined angle to a substrate surface of the liquid crystal display panel. In such a liquid crystal display device, while a hue of light entering in a vertical direction to a substrate surface of the liquid crystal display panel is substantially not changed, a hue of light entering in an oblique direction to the substrate surface is changed so as to compensate change in hue caused by a liquid crystal layer. Consequently, a difference hardly occurs between a hue seen from a visual point in a vertical direction to a substrate surface and a hue seen from a visual point in a direction oblique to the vertical direction.